Conventionally, there is known a technique of additionally registering a word that is not registered in a word dictionary in accordance with a user's correction operation on a recognition result in a voice recognition system that performs voice recognition processing using a word dictionary. In this conventional technique, when the word corrected by the user is not registered in a word dictionary, the corrected word is additionally registered in the word dictionary automatically. For this reason, words that may affect the voice recognition processing adversely when registered in the word dictionary may be registered additionally, which needs to be improved.